I really liked Dante's Inferno. Played it AFTER I Platinumed GOW3 and still had a blast so go for it. It's not that expensive right now. Might even want to rent it instead. Shouldn't take you more than 6-7 days tops to Platinum.

I think God of War 3 looks better and is a better experience but Dante's Inferno certainly plays better and has more options, I use cross attacks much more often than Death's Scythe unlike in Gow where i just use the blades mainly

Yeah, you can use the blades for all of GoW III except for using the Gauntlets for bosses by the end of the game. The other two weapons are there just to move along the story and don't really give much gameplay variety.